A5016028348- GaN-based semiconductor devices and materials
- Ga2O3 and related materials
- Semiconductor Quantum Structures and Devices
- Photocathodes and Microchannel Plates
- Silicon Carbide Semiconductor Technologies
- ZnO doping and properties
- Oceanographic and Atmospheric Processes
- Climate variability and models
- Semiconductor materials and devices
- Thermal properties of materials
- Meteorological Phenomena and Simulations
- Ocean Acidification Effects and Responses
- Metal and Thin Film Mechanics
- Geological and Geophysical Studies
- Tropical and Extratropical Cyclones Research
- Electronic and Structural Properties of Oxides
- Semiconductor materials and interfaces
- Advanced Semiconductor Detectors and Materials
- Acoustic Wave Resonator Technologies
- Marine and Coastal Research
- Advanced Thermoelectric Materials and Devices
- Photonic Crystals and Applications
- Integrated Circuits and Semiconductor Failure Analysis
- Advanced Photocatalysis Techniques
- Methane Hydrates and Related Phenomena
DEVCOM Army Research Laboratory
2023-2024
United States Army Combat Capabilities Development Command
2024
Georgia Institute of Technology
2012-2023
Oak Ridge National Laboratory
2020-2021
AID Atlanta
2020
LG (South Korea)
2018
Pennsylvania State University
2018
University of North Carolina at Charlotte
2017
Compound Semiconductor Centre (United Kingdom)
2015
National Oceanic and Atmospheric Administration
1995-2002
This study investigates the predictability of seasonal mean circulation anomalies associated purely with influence anomalous sea surface temperatures (SSTs). Within this framework, atmospheric on a case by basis are understood to consist potentially predictable boundary-forced component and an unpredictable naturally varying component. The predictive capability general model (AGCM) for timescales should therefore be assessed in terms average skill over many cases, since it is only then that...
Data and analysis are presented for the study of efficiency droop in visible III-nitride light-emitting diodes (LEDs) considering effects both electron spill-over out active region hole injection into region. Performance characteristics blue LEDs with lattice-matched In0.18Al0.82N electron-blocking layers (EBLs) different thicknesses were measured order to exclude strain doping EBL, quantum efficiencies analyzed taking account current relative concentration. The results suggest that highest...
Abstract Current understanding of phonons treats them as plane waves/quasi-particles atomic vibration that propagate and scatter. The problem is conceptually, when any level disorder introduced, whether compositional or structural, the character vibrational modes in solids changes, yet nearly all theoretical treatments continue to assume are still waves. For example, phonon contributions alloy thermal conductivity (TC) rely on this assumption most often computed from virtual crystal...
Large-size vertical β-Ga <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Schottky barrier diodes (SBDs) with various device areas were demonstrated on a Si-doped n-type drift layer grown by hydride vapor phase epitaxy (HVPE) bulk Sn-doped (001) substrate. In this letter, the devices have two circular contacts diameter of 1500 and 500 μm square dimensions 1600 × <sup...
In this study, various thermal characterization techniques and multi-physics modeling were applied to understand the characteristics of GaN vertical quasi-vertical power diodes. Optical thermography typically used for lateral device temperature assessment including infrared thermography, thermoreflectance imaging, Raman thermometry p-i-n diodes determine if each technique is capable providing insight into devices. Of these techniques, imaging nanoparticle assisted proved yield accurate...
Ultraviolet (UV) avalanche photodiodes (APDs) based on Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> Ga xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> N wide-bandgap semiconductor alloys (x = 0.05) are reported. The epitaxial structure was grown by metalorganic chemical vapor deposition a GaN substrate having low dislocation density. Step graded n-type Si-doped layers 0 and 0.02) were introduced instead of thick n-Al...
GaN p-i-n ultraviolet avalanche photodiodes (UV-APDs) were fabricated from epitaxial structures grown on low-dislocation-density free-standing substrates to form 4 × UV-APD arrays with a device size of 75 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . The devices in the array showed uniform and reliable distribution breakdown voltage (V <sub xmlns:xlink="http://www.w3.org/1999/xlink">BR</sub> ) leakage current density. average V 16...
We compare the performance characteristics of Al0.05Ga0.95N UV avalanche photodiodes (APDs) grown on different substrates. UV-APDs a free-standing GaN substrate show lower dark-current densities for all fabricated mesa sizes than similar GaN/sapphire template. In addition, stable gain higher 5 × 105 and significant increase in responsivity are observed. believe that high crystalline quality with low dislocation density is responsible observed leakage currents, characteirstics, reliability devices.
Front-illuminated GaN-based separate absorption and multiplication (SAM) ultraviolet (UV) avalanche photodiodes (APDs) with various photon detection areas are demonstrated grown by metalorganic chemical vapor deposition on bulk GaN native substrates low dislocation density. By adopting a front-illuminated UV-APD structure thin AlGaN window layer, no additional etching of the substrate for reduction strong UV is required. The epitaxial layer p-i-p-i-n SAM UV-APDs consists Mg-doped p-Al <sub...
We report on III–nitride (III–N) avalanche phototransistor (APT) action by illuminating ultraviolet (UV) photons onto a GaN/InGaN npn heterojunction bipolar transistor in an open-base configuration. A high responsivity of >1 A/W was measured for the device operating at collector-to-emitter voltage (VCE) <15 V mode. The carrier multiplication reversed biased collector leads to photocurrent as VCE increases. At λ = 380 nm, APT shows >68 95 V. InGaN demonstrates feasibility using III–N...
We report vertical GaN p-i-n rectifiers grown on a bulk substrate. These planar were implemented with Schottky field plates and buried-junction terminations using ion implantation as mean of device isolation. The 1130-μm-diameter achieved blocking voltage (BV) 1.2 kV an ON-state current drive 10 A. A temperature-dependent OFF-state study showed that the variable-range-hopping (VRH) conduction is dominant for devices operating at temperature less than 160 K, multistep electron transition...
We report a homojunction gallium nitride (GaN) p-i-n rectifier fabricated on free-standing GaN substrates with the breakdown voltage 800 V and low specific ON-resistance (R <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ON</sub> A). At 298 K, RONA is 0.28 mΩ-cm <sup xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at current density (J) of 2.5 kA/cm corresponding Baliga's figure merit GW/cm . given temperature, R A values decrease J due to...
Ensembles of extended Atmospheric Model Intercomparison Project (AMIP) runs from the general circulation models National Centers for Environmental Prediction (formerly Meteorological Center) and Max-Planck Institute (Hamburg, Germany) are used to estimate potential predictability (PP) an index Pacific–North America (PNA) mode climate change. The PP this pattern in “perfect” prediction experiments is 20%–25% index’s variance. models, particularly that MPI, capture virtually all variance their...
A high-sensitivity 4H–SiC temperature sensor and an alpha detector have been fabricated using additively printed metal contacts. The surface morphology electrical conductivity of the electrodes were established prior to Schottky diode development. diodes with direct-write silver contacts on 5 μm-thick epilayer characterized electrically in terms forward reverse current–voltage high-frequency capacitance–voltage characteristics. turn-on voltage diodes, as from characteristics measured up a...
We report on the direct patterning of two-dimensional periodic structures in GaN-based light-emitting diodes (LEDs) through laser interference ablation for fast and reliable fabrication micro- nano-structures aimed at enhancing light output. Holes arranged a hexagonal lattice array having an opening size 500 nm, depth 50 periodicity 1 μm were directly formed by three-beam without photolithography or electron-beam lithography processes. The laser-patterned LEDs exhibit enhancement output...
Free-standing gallium nitride (GaN) substrates are in high demand for power devices, laser diodes, and high-power light emitting diodes (LEDs). SixPoint Materials Inc. has begun producing 2” GaN through our proprietary Near Equilibrium AmmonoThermal (NEAT) growth technology. In a single 90 day growth, eleven c-plane boules were grown from free-standing hydride vapor phase epitaxy (HVPE) substrates. The had an average X-ray rocking curve full width at half maximum (FWHM) of 33 ± 4 the 002...
In this work, we report a polarized Raman study on the vibrational properties of InAs/InAs1-xSbx SLs as well selected InAs1-xSbx alloys, all grown GaSb substrates by either MBE or MOCVD, from both growth surface and cleaved edge.
The value of assimilated subsurface oceanic data to statistical predictions interannual variability sea surface temperature (SST) at the National Centers for Environmental Prediction (NCEP) is shown. Subsurface tropical Pacific Ocean come from ocean analysis July 1982 June 1993 and a numerical model forced by observed wind stress 1961 1982. on operational NCEP canonical correlation (CCA) forecasts SST assessed. CCA first run using only level pressure as predictors, then are added. It found...
We report state-of-the-art d.c. and RF performance of GaN/InGaN npn DHBTs grown by the MOCVD technology on sapphire substrates. The fabricated HBTs achieved a collector current density greater than 50 kA/cm 2 gain 60 at voltage 13 V. A open-base collector-emitter breakdown 90 V was measured. Using same layer structure device fabrication techniques, we also demonstrated with f T 8 GHz max 1.8 11 . These measurement results capability feasibility III-N for high-power circuit applications.